Qualification > Sciences

Physics Help HERE ONLY !!

<< < (165/173) > >>

lana:
exactly 1 - is 0.5 and 2- is 7.68 i'm sorry your work is not right but + rep for u anyway thanks

hmh:

--- Quote from: lana on June 09, 2009, 09:53:44 pm ---exactly 1 - is 0.5 and 2- is 7.68 i'm sorry your work is not right but + rep for u anyway thanks

--- End quote ---

i dnt want +reps lol.. i want to help. srry i misunderstood them.. now i jst corrected... u can check bak :)

MR.BooMBastiC:
u want me 2 explain!!!!

i wrote da value wring by mistake!

i hav corrected it

best of luck mate!!

lana:
ooh thanks both of you ur both so sweet =]
+ rep 4 u  =p
and best of luck for u 2 !!! =]

Bani:

--- Quote from: hmh on June 09, 2009, 09:49:15 pm ---
--- Quote from: lana on June 09, 2009, 09:44:13 pm ---hi ... !! ok i have two questions it's from past papers June and November 03 :

1- the mass of a full bottle of cooking oil is 1.3 kg when exactly half the oil is used  the mass of the bottle and the remaining oil is 0.9 kg what is the mass of the bottle ? now i know it's ''B'' but how ??

2- the half life of a radioactive substance is 5 hours a sample is tested and found to contain 0.48 g of the substance how much of the substance was present in the sample 20 hours before the sample was tested ?? i also know its ''D'' but again how ??

thanks and +rep for anyone who answers =]

--- End quote ---

For no.1 : first find the mass of the half of oil( 1.3-0.9=0.4), then u know that other half is 0.4 too. So, subtract the whole mass of oil (0.4*2) from the mass of bottle and oil (1.3) to get 0.5kg
For no. 2: Half life(time for value to half) is 5 hours, and there are 4  5s in 20(meaning you'll have to multiply 0.48 by 2  4 times to get the value 20 hours before decay
so, finally, you'll get 7.68g

I hope this helped

OK so 1 is B i dnt knw the value because i didnt look at exam but shud be 0.25kg becuz.. 1.3/2 = 0.65 half left... but we got 0.9 kg as mass so 0.9-0.65 = 0.25 kg mass of bottle.

2 .. again didnt look at the paper.. but guessesing tht answer shd be 1.92g... as 4 half lives reversed as of 5 hrs 1 time.. so 0.48*4 = 1.92.

--- End quote ---

Navigation

[0] Message Index

[#] Next page

[*] Previous page